The present invention relates to differential drives for a motor vehicle, and more particularly, relates to a speed sensing torque transfer device for use in a vehicle.
The differential drive is well known in the motor vehicle industry. The differential drive is used in conjunction with the transmission and drive shaft or propeller shaft (prop shaft) to turn the automotive vehicle wheels at different speeds when the vehicle is going around a curve, to differentiate the speed of each wheel individually and to provide the proper amount of torque to each wheel in slipping, turning or other road to wheel conditions.
In a traditional torque on demand drive train layout of an automotive vehicle, there is a primary driven front/rear axle and a secondary driven hang-on axle that is connected via prop shaft or drive shaft and a torque transferring coupling to the primary driven axle. The torque transfer coupling is usually directly in front of the secondary driven axle. The axle differential creates the division of power or torque to each side shaft of the axle. The primary driven axle also includes a differential which divides the necessary power to the side shaft of each front axle and then the wheels. The division of torque between the front and rear axle is completed by the torque transfer coupling which is a separate unit on the drive train system and requires spacing for its housing and other related parts. A current state-of-the-art passive torque transfer coupling for an automotive vehicle is located between the primary and secondary driven axles of the vehicle and can generally consist of a viscous coupling, gear rotor coupling, or any other passive speed sensing device. The viscous coupling unit senses slip conditions of the wheels, monitors current driving conditions of the vehicle and distributes torque to each wheel or axle as necessary.
A passive torque transfer system provides flexibility in the distribution of torque between the axles in an all-wheel or four-wheel drive automotive system. Generally, a passive speed sensing device will provide traction control through a smooth and progressive torque transfer to the wheel or axle with the greatest traction potential. The viscous coupling is a well known passive speed sensing device that operates according to principles of fluid friction and thus is dependent on speed differences. Furthermore, the viscous coupling has great flexibility in its design parameters thus allowing it to achieve desired torque characteristics with relation to traction and handling. The viscous coupling is a self contained unit that does not need electronics or remote sensors to operate. All of these passive speed sensing torque drive systems are located in a separate housing usually directly in front of the rear differential.
Therefore, there is a need in the art for a device to simplify, reduce the weight and required space of a passive speed sensing torque distribution device for use in an automotive vehicle.
One object of the present invention is to provide an improved torque distribution device. Another object of the present invention is to provide a torque distribution device that includes a viscous transmission that runs at axle speed, which will reduce imbalance issues in the transaxle.
Yet a further object of the present invention is to reduce and minimize the packaging requirements in the prop shaft area of the automotive vehicle.
Still another object of the present invention is to provide a differential that includes a viscous transmission that runs in oil and also reduces the effort for bearings and seals while improving the cooling of the differential.
A further object of the present invention is to reduce the number of interfaces in the drive train while also reducing the weight and cost of the drive train assembly.
Still a further object of the present invention is to integrate within the existing axle housing the viscous transmission to control the torque between the front and rear axles.
To achieve the foregoing objects the differential drive for use on a vehicle includes a rotatably driven differential housing supported in a housing. A differential gear set arranged and supporting in the differential housing. The differential gear set including at least two side shaft gears and at least two side gears. A torque distribution device having a viscous transmission. The viscous transmission having an inner hub and an outer casing. The inner hub being connected to a first side shaft. The viscous transmission also includes an outer casing that is connected to one of the side shaft gears. The viscous transmission connects the output of the first side shaft to one of the side shaft gears.
One advantage of the present invention is a new and improved torque distribution device for a vehicle.
A further advantage of the present invention is that the torque distribution device uses a viscous transmission that runs at axle speed which reduces imbalance issues on the drive train.
A further advantage of the present invention is the reduced or minimized packaging requirement in the prop shaft area of the motor vehicle.
Yet a further advantage of the present invention is the inclusion of the viscous transmission that runs in oil to reduce the effort for bearings and seals while also improving the cooling within the differential.
A further advantage of the present invention is to reduce the number of interfaces and reduce the weight and costs of distributing torque to the drive train system.
A further advantage of the present invention is the integration within the housing of the viscous transmission for the torque distribution device.
Other objects, features, and advantages of the present invention will become apparent from the subsequent description and appended claims taken in conjunction with the accompanying drawings.